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CHAPTER 17
SEXUALLY TRANSMITTED DISEASES
BEHAVIORAL OBJECTIVES
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Describe the structure of a virus. [17.1, p.340, Fig. 17.2]
Describe the life cycle of a DNA virus. [17.1, pp.340-341, Fig. 17.3]
Name the causative agents for AIDS, genital warts, and genital herpes. [17.1, pp.342-343]
Discuss the stages of HIV infection, how the disease can be treated, and how to prevent its occurrence. [17.1,
p.342]
Describe the symptoms of a genital herpes infection. [17.1, p.343]
Distinguish between strains of hepatitis, and know which is transmitted through sexual contact. [17.1, p.344]
Describe the structure and the life cycle of a bacterium. [17.2, p.345, Fig. 17.6]
Understand how bacteria reproduce. [17.2, p. 346, Fig. 17.7]
Understand the methods for preventing the spread of infectious bacteria. [17.2, p.346]
Name the causative agents for chlamydia, gonorrhea, and syphilis. [17.2, pp.347-349]
Describe the symptoms of chlamydia in the male and in the female, and compare this disease to a gonorrheal
infection. Tell how it is treated. [17.2, pp.346-348]
Describe the symptoms of a gonorrheal infection in the male and in the female and how they are treated. [17.2,
p.348, Figs. 17.10 & 17.11]
Define pelvic inflammatory disease, and describe how it affects reproduction. [17.2, p.348]
Describe the three stages of syphilis and how it is treated. [17.2, p.349, Fig. 17.12]
Describe how a newborn becomes infected with herpes, gonorrhea, chlamydia, or syphilis. [p. 344, 348, 349]
List other common sexually transmitted diseases and describe the associated symptoms. [17.3, p.351, Figs.
17.13 & 17.14. Table 17.3]
Understand and use the bold-faced and italicized terms included in this chapter. [Understanding Key Terms,
p.353]
EXTENDED LECTURE OUTLINE
17.1 Viral Infectious Diseases
Pathogens are organisms that cause disease. Sexually transmitted diseases (STDs) are contagious diseases spread by
pathogens transmitted from one person to the next through sexual contact. Some STDs are caused by viruses.
Viruses cannot live independently and take over the host cell’s machinery to produce more copies of themselves.
Viruses are noncellular particles made up of an outer proteinaceous capsid and an inner core of nucleic acid. Viruses
contain DNA or RNA. Viruses generally infect a host cell by binding to the plasma membrane, penetrating the cell,
replicating viral genetic material using the host’s machinery, producing and assembling viral proteins, and building
new viruses.
Some viruses enter a period of latency after entering the host cells, during which they are not actively producing
symptoms in the host. Environmental factors and stress can trigger these viruses to again become active.
Latent viruses can alter host cell chromosomes, triggering the development of cancer, as in the human
papillomavirus causing cervical cancer.
Sexually transmitted diseases that are caused by viruses require intimate contact to be transmitted from one
individual to the next. Antibiotics have no effect on viral illnesses.
HIV Infections
Two types of human immunodeficiency virus (HIV) are known: HIV-2 is pandemic in Africa, and several varieties
of HIV-1 are prevalent in the United States. In the US, most new HIV infections occur in minority women. It is
estimated that 34.3 million people worldwide may be infected with HIV, with especially high rates in Africa.
HIV has a specificity for helper T cells. During first stage, there are no symptoms, and people do not know they
carry HIV. Later, T lymphocyte counts begin to fall. In the last stage, known as AIDS, individuals become infected
with opportunistic infections as their immune systems collapse. Most people die from opportunistic infection, not
AIDS itself.
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A treatment called highly active antiretroviral therapy (HAART) that combines reverse transcriptase inhibitors and a
protease inhibitor has proven to be effective in many instances. There is no cure for AIDS.
Genital Warts
Human papillomaviruses (HPVs) cause warts, including genital warts which are sexually transmitted. Over 1 million
people contract this virus annually.
Transmission and Symptoms
Many carriers have no symptoms, or warts may be flat and scalelike. Newborns can become infected as
they pass through the birth canal. Genital warts are associated with cervical cancer, which is on the rise in
teens.
Treatment
There is no cure for genital warts, but they can be treated with laser or cryosurgery. Use of a condom with
nonoxynol-9 is recommended to prevent the spread of genital warts.
Herpes Infections
Herpes viruses are responsible for a variety of human illnesses, from chicken pox to shingles to cold sores and
mononucleosis.
Cold Sores and Fever Blisters
Herpes simplex type 1 is responsible for cold sores, and herpes simplex type 2 causes genital herpes. Type
1 may be transmitted to the genitals through active cold sores.
Genital Herpes
At least 1 million new cases of genital herpes (caused by herpes simplex type II) appear each year, many of
which have few symptoms. Fever blisters may appear on the genitals and leave painful ulcers. There may
be fever and pain on urination. After the initial outbreak heals, the virus is latent until stress or
environmental influences cause its recurrence. Infection of newborns through active lesions can lead to
blindness, brain damage, or death.
Transmission
Herpes lesions shed active viruses, so all contact with lesions should be avoided.
Treatment
There is no cure for genital herpes, but some drugs disrupt viral reproduction.
Hepatitis Infections
Hepatitis A is carried in sewage-contaminated drinking water and can also be transmitted through sexual contact.
Hepatitis C is the post-transfusion form of hepatitis, which can lead to liver cancer and death. Other types of
hepatitis are also under investigation.
Hepatitis B
Hepatitis B is highly contagious and is usually spread by sexual contact. Hepatitis B is spread in the same
manner as HIV, and most people with HIV have this. About half of those infected experience flulike
symptoms and jaundice. Some have an acute infection from which they recover; others get the chronic form
that can lead to liver failure.
There is no treatment for hepatitis B, although a vaccine is now available.
Mader VRL CD-ROM
Image 0324l.jpg (Fig. 17.1)
Image 0325l.jpg (Fig. 17.2)
Image 0326l.jpg (Fig. 17.3)
Image 0327l.jpg (Fig. 17.4)
Image 0328l.jpg (Fig. 17.5)
Mader ESP Modules Online
Diversity/Viruses/Characteristics
Case Studies Online
AIDS Vaccine
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Transparencies
252 (Fig. 17.2a)
253 (Fig. 17.3)
254 (Fig. 17.4)
255 (Fig. 17.5)
17.2 Bacterial Infectious Diseases
Most bacteria are free-living organisms that reproduce asexually by binary fission. Many perform useful services in
the digestive tract and are a part of the normal microbial flora. Bacterial diseases can be passed directly from one
person to the next and can be controlled by hand washing and “safe sex” methods. Bacterial diseases respond to
antibiotic therapy.
Chlamydia
Chlamydia is caused by a tiny bacterium that enters cells by endocytosis. New chlamydial infections are more
frequent than any other STD because many cases go undetected.
Symptoms
Usually, symptoms are mild, such as a burning sensation upon urination and a discharge in men. Women
have symptoms similar to urinary tract infections and can be treated with the wrong antibiotics.
Chlamydial infection can lead to pelvic inflammatory disease (PID) in women, a painful condition that can
result in sterility.
Diagnosis and Treatment
New tests are available for diagnosis of chlamydia, and it can be cured with tetracycline, among other
antibiotics.
Gonorrhea
Gonorrhea is caused by a bacterium, and its incidence has declined. The infection rate is greater among African
Americans and women using the birth control pill.
Symptoms
Symptoms in males are more obvious; usually, painful urination is the first clue. Most women are
asymptomatic, which can lead to PID. Eye infection can lead to blindness as an infant passes through the
birth canal.
Transmission and Treatment
Gonorrhea can be transmitted through sexual contact. Blood tests are being developed, but discharge needs
to be examined to identify this bacterium as present. Antibiotics can clear up an infection, although
resistant strains are surfacing.
Syphilis
Syphilis is caused by the bacterium Treponema palladium and is on the decline. This disease has three stages, the
first of which involves a hard chancre at the site of infection. The second stage occurs after a latent period and
involves a systemic rash. Another latent period follows, and in some people, a third stage is seen, during which the
disease progresses throughout the body and weakens arterial walls. Death eventually follows.
Diagnosis and Treatment
Blood tests and microscopic examination of fluids from lesions can confirm the presence of this pathogen.
Penicillin can cure syphilis in any stage.
Mader VRL CD-ROM
Image 0329l.jpg (Fig. 17.6)
Image 0330l.jpg (Fig. 17.7)
Image 0331l.jpg (Fig. 17.8)
Image 0332l.jpg (Fig. 17.9)
Image 0333l.jpg (Fig. 17.10)
Image 0334l.jpg (Fig. 17.11)
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Mader VRL CD-ROM, con’t.
Image 0335al.jpg (Fig. 17.12)
Image 0335bl.jpg (Fig. 17.12)
Image 0336l.jpg (Fig. 17A)
Transparencies
256 (Fig. 17.6)
257 (Fig. 17.7)
258 (Fig. 17.8)
259 (Fig. 17.9)
260 (Fig. 17.10)
261 (Fig. 17.12a)
17.3 Other Infectious Diseases
Organisms in the kingdoms Protista, Fungi, and Animalia can also cause sexually transmitted diseases.
Infectious Diseases Caused by Protozoa
A protozoan causes a form of vaginitis, called trichomoniasis, in women.
Infectious Diseases Caused by Fungi
The yeast Candida albicans, usually present in the vagina, can sometimes increase beyond normal, producing
vaginitis.
Infectious Diseases Caused by Animals
Pubic Lice (Crabs)
The parasitic crab louse causes pubic lice. Pubic lice can be contracted by direct contact with an infected
person or by contact with his or her clothing. Medications can kill the lice, and all clothing and bedding
should be washed by machine in hot water.
Mader VRL CD-ROM
Image 0337l.jpg (Fig. 17.13)
Image 0338l.jpg (Fig. 17.13)
Image 0339l.jpg (Fig. 17.14)
Image 0340l.jpg (Fig. TA17.1)
Mader ESP Modules Online
Diversity/Invertebrates/Arthropods
Transparencies
262 (Fig. TA17.1)
SEVENTH EDITION CHANGES
New/Revised Text:
This was chapter 16 in the previous edition. The chapter has been revised to include non-sexually
transmitted infectious diseases caused by viruses, bacteria, fungi, and other animals. Statistics of new cases of AIDS
and other STDs have been updated to reflect the most current information from the Centers of Disease Control.
17.1 Viral Infectious Diseases (previously Viral in Origin) has been rewritten and the discussion of the
typical DNA animal virus life cycle has been simplified for better understanding; Figure 17.3 illustrating this life
cycle has also been simplified. The discussion of HIV infections summarized and identifies types and subtypes of
HIV found in Africa and in the United States. HIV infections and AIDS are covered in detail in the AIDS
supplement.
17.2 Bacterial Infectious Diseases (previously Bacterial in Origin). All statistics have been updated.
17.3 Other Infectious Diseases (previously Other Sexually Transmitted Diseases) has been rewritten and
includes a more detailed introduction to kingdoms Protista, Fungi, and Animalia, and how these organisms transmit
infectious diseases. Several diseases caused by protozoa are discussed. There is a new topic on infectious diseases
caused by fungi. The topic on infectious diseases caused by animals discusses head lice and parasitic worms, as
well as pubic lice.
New Bioethical Focus: HIV Vaccine Testing in Africa
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New/Revised Figures:
17.3 Life cycle of an animal DNA virus; 17.4 Genital warts; 17.5 Genital herpes; 17.8 Chlamydial
infection; 17.10 Gonorrhea; 17.12 Syphilis; 17A AIDS in Africa; 17.13 Organisms that cause vaginitis; 17.14
Sexually transmitted animal
New/Revised Tables:
17.1 Infectious Diseases Caused by Viruses (revised); 17.2 Infectious Diseases Caused by Bacteria
(revised); 17.3 Infectious Diseases Caused by Protozoa, Fungi, and Animals (new).
STUDENT ACTIVITIES
HIV Vaccine Testing in Africa
1. Read aloud the Bioethical Focus “HIV Vaccine Testing in Africa” (p. 350). Then address the questions from the
Bioethical Focus. Point out to students that it is important for them to develop informed opinions about topics
that affect the health of so many people.
Brochures on STDs
2. Ask certain students to visit the nearest public health clinic (often this is a county health department) and pick up
a few copies of every brochure they distribute on sexually transmitted diseases. If there is a “free AIDS clinic”
in your area, do the same there. (If you ask, the people at these clinics may give you enough brochures for each
member of the class.)
Student Survey
3. Construct a survey to discover how many of the STDs the class is familiar with before they read this chapter
(include AIDS, syphilis, chlamydia, gonorrhea, genital warts and other herpes infections, etc.). Ask your
students how much information they have received about STDs and where that information came from. Tally
student responses on the chalkboard. Include in the survey other information like which of these can be cured
and which cannot. After giving the survey, ask the class to “grade” their own survey as the class discusses it.
Finally provoke them to conclude their knowledge is inadequate.
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